Myrtucommulones and Related Acylphloroglucinols from Myrtaceae as a Promising Source of Multitarget SARS-CoV-2 Cycle Inhibitors.

The LABEXTRACT plant extract bank, featuring diverse members of the Myrtaceae family from Brazilian hot spot regions, provides a promising avenue for bioprospection. Given the pivotal roles of the Spike protein and 3CLpro and PLpro proteases in SARS-CoV-2 infection, this study delves into the correlations between the Myrtaceae species from the Atlantic Forest and these targets, as well as an antiviral activity through both in vitro and in silico analyses. The results uncovered notable inhibitory effects, with Eugenia prasina and E. mosenii standing out, while E. mosenii proved to be multitarget, presenting inhibition values above 72% in the three targets analyzed. All extracts inhibited viral replication in Calu-3 cells (EC50 was lower than 8.3 µg·mL-1). Chemometric analyses, through LC-MS/MS, encompassing prediction models and molecular networking, identified potential active compounds, such as myrtucommulones, described in the literature for their antiviral activity. Docking analyses showed that one undescribed myrtucommulone (m/z 841 [M - H]-) had a higher fitness score when interacting with the targets of this study, including ACE2, Spike, PLpro and 3CLpro of SARS-CoV-2. Also, the study concludes that Myrtaceae extracts, particularly from E. mosenii and E. prasina, exhibit promising inhibitory effects against crucial stages in SARS-CoV-2 infection. Compounds like myrtucommulones emerge as potential anti-SARS-CoV-2 agents, warranting further exploration.

Immunoglobulin A as a Key Immunological Molecular Signature of Post-COVID-19 Conditions.

COVID-19 has infected humans worldwide, causing millions of deaths or prolonged symptoms in survivors. The transient or persistent symptoms after SARS-CoV-2 infection have been defined as post-COVID-19 conditions (PCC). We conducted a study of 151 Brazilian PCC patients to analyze symptoms and immunoglobulin profiles, taking into account sex, vaccination, hospitalization, and age. Fatigue and myalgia were the most common symptoms, and lack of vaccination, hospitalization, and neuropsychiatric and metabolic comorbidities were relevant to the development of PCC. Analysis of serological immunoglobulins showed that IgA was higher in PCC patients, especially in the adult and elderly groups. Also, non-hospitalized and hospitalized PCC patients produced high and similar levels of IgA. Our results indicated that the detection of IgA antibodies against SARS-CoV-2 during the course of the disease could be associated with the development of PCC and may be an immunological signature to predict prolonged symptoms in COVID-19 patients.

In silico screening of phenylethanoid glycosides, a class of pharmacologically active compounds as natural inhibitors of SARS-CoV-2 proteases.

Since the advent of Covid-19, several natural products have been investigated regarding their in silico interactions with SARS-CoV-2 proteases - 3CLpro and PLpro, two of the most important pharmacological targets for antiviral development. Phenylethanoid glycosides (PG) are a class of natural products present in important medicinal plants and a drug containing this group of active ingredients has been successfully used in the treatment of Covid-19 in China. Thus, a dataset with 567 derivatives of this class was built from reviews published between 1994 and 2020, and their interaction against both SARS-CoV-2 proteases was investigated. The virtual screening was performed by filtering the PGs through the evaluation of scores based on the AutoDock Vina, GOLD/ChemPLP, and GOLD/GoldScore evaluation functions. The bRO5 pharmacokinetic parameters of the PGs ranked in the previous step were analyzed and their interaction with key amino acid residues of the 3CLpro and PLpro enzymes was evaluated. Ninety-eight compounds were identified by computational approaches against PLpro and 80 PGs against 3CLpro. Of these, four interacted with key catalytic residues of PLpro, which is an indicative of inhibitory activity, and three compounds interacted with catalytic key residues of 3CLpro. Of these, five PGs occur in plants of the Traditional Chinese Medicine (TCM), while two are components of plants/formulations currently used in the Covid-19 protocols in China. The data presented here show the potential of PGs as selective inhibitors of SARS-CoV-2 3CLpro and PLpro.

Genomic surveillance and sequencing of SARS-CoV-2 across South America.

After 2 years of the COVID-19 pandemic, the protocols used to control infection lack attention and analysis. We present data about deposits of complete genomic sequences of SARS-CoV-2 in the Global Initiative on Sharing All Influenza Data (GISAID) database made between January 2021 and May 31, 2022. We build the distribution profile of SARS-CoV-2 variants across South America, highlighting the contribution and influence of each variant over time. Monitoring the genomic sequences in GISAID illustrates negligence in the follow up of infected patients in South America and also the discrepancies between the number of complete genomes deposited throughout the pandemic by developed and developing countries. While Europe and North America account for more than 9 million of the genomes deposited in GISAID, Africa and South America deposited less than 400 000 genome sequences. Genomic surveillance is important for detecting early warning signs of new circulating viruses, assisting in the discovery of new variants and controlling pandemics.

Tras dos años de pandemia del COVID-19, los protocolos empleados para controlar la infección carecen de atención y análisis. En este artículo se presentan datos sobre depósitos de secuencias genómicas completas del SARS-CoV-2 en la base de datos de secuenciación GISAID, la Iniciativa mundial para intercambiar todos los datos sobre la gripe aviar, realizadas entre enero del 2021 y el 31 de mayo del 2022. Se creó el perfil de distribución de las variantes del SARS-CoV-2 en América del Sur, en el que se destacaron la contribución y la influencia de cada variante a lo largo del tiempo. El monitoreo de las secuencias genómicas en GISAID ilustra la negligencia en el seguimiento de los pacientes infectados en América del Sur, así como las discrepancias entre el número de genomas completos depositados a lo largo de la pandemia por parte de los países desarrollados y los países en desarrollo. Mientras que Europa y América del Norte han depositado más de 9 millones de genomas en GISAID, África y América del Sur han aportado menos de 400 000 secuencias genómicas. La vigilancia genómica es importante para detectar los primeros signos de alerta de virus nuevos en circulación, ayudar en el descubrimiento de nuevas variantes y controlar las pandemias.

Após 2 anos da pandemia de covid-19, os protocolos usados para controlar a infecção necessitam maior atenção e análise. Apresentamos dados sobre as sequências genômicas completas do SARS-CoV-2 depositadas no banco de dados do a iniciativa internacional para o intercâmbio de dados sobre os vírus da influenza (GISAID) entre janeiro de 2021 e 31 de maio de 2022. Construímos o perfil de distribuição das variantes do SARS-CoV-2 na América do Sul, destacando a contribuição e a influência de cada variante ao longo do tempo. O monitoramento das sequências genômicas do GISAID ilustra a negligência no acompanhamento de pacientes infectados na América do Sul e as discrepâncias entre os países desenvolvidos e em desenvolvimento com relação ao número de genomas completos depositados ao longo da pandemia. Enquanto a Europa e a América do Norte respondem por mais de 9 milhões dos genomas depositados no GISAID, a África e a América do Sul depositaram menos de 400 000 sequências genômicas. A vigilância genômica é importante para detectar sinais de alerta precoces de novos vírus circulantes, auxiliar na descoberta de novas variantes e controlar pandemias.

How legislations affect new taxonomic descriptions.

Restrictions placed on the distribution of biological material by the legislation of countries such as India, South Africa, or Brazil exclude strains that could serve as type material for the validation or valid publication of prokaryotic species names. This problem goes beyond prokaryotic taxonomy and is also relevant for other areas of biological research.

Genomic surveillance and sequencing of SARS-CoV-2 across South America / Vigilancia genómica y secuenciación del SARS-CoV-2 en América del Sur / Vigilância genômica e sequenciamento do SARS-CoV-2 na América do Sul

ABSTRACT After 2 years of the COVID-19 pandemic, the protocols used to control infection lack attention and analysis. We present data about deposits of complete genomic sequences of SARS-CoV-2 in the Global Initiative on Sharing All Influenza Data (GISAID) database made between January 2021 and May 31, 2022. We build the distribution profile of SARS-CoV-2 variants across South America, highlighting the contribution and influence of each variant over time. Monitoring the genomic sequences in GISAID illustrates negligence in the follow up of infected patients in South America and also the discrepancies between the number of complete genomes deposited throughout the pandemic by developed and developing countries. While Europe and North America account for more than 9 million of the genomes deposited in GISAID, Africa and South America deposited less than 400 000 genome sequences. Genomic surveillance is important for detecting early warning signs of new circulating viruses, assisting in the discovery of new variants and controlling pandemics.

RESUMEN Tras dos años de pandemia del COVID-19, los protocolos empleados para controlar la infección carecen de atención y análisis. En este artículo se presentan datos sobre depósitos de secuencias genómicas completas del SARS-CoV-2 en la base de datos de secuenciación GISAID, la Iniciativa mundial para intercambiar todos los datos sobre la gripe aviar, realizadas entre enero del 2021 y el 31 de mayo del 2022. Se creó el perfil de distribución de las variantes del SARS-CoV-2 en América del Sur, en el que se destacaron la contribución y la influencia de cada variante a lo largo del tiempo. El monitoreo de las secuencias genómicas en GISAID ilustra la negligencia en el seguimiento de los pacientes infectados en América del Sur, así como las discrepancias entre el número de genomas completos depositados a lo largo de la pandemia por parte de los países desarrollados y los países en desarrollo. Mientras que Europa y América del Norte han depositado más de 9 millones de genomas en GISAID, África y América del Sur han aportado menos de 400 000 secuencias genómicas. La vigilancia genómica es importante para detectar los primeros signos de alerta de virus nuevos en circulación, ayudar en el descubrimiento de nuevas variantes y controlar las pandemias.

RESUMO Após 2 anos da pandemia de covid-19, os protocolos usados para controlar a infecção necessitam maior atenção e análise. Apresentamos dados sobre as sequências genômicas completas do SARS-CoV-2 depositadas no banco de dados do a iniciativa internacional para o intercâmbio de dados sobre os vírus da influenza (GISAID) entre janeiro de 2021 e 31 de maio de 2022. Construímos o perfil de distribuição das variantes do SARS-CoV-2 na América do Sul, destacando a contribuição e a influência de cada variante ao longo do tempo. O monitoramento das sequências genômicas do GISAID ilustra a negligência no acompanhamento de pacientes infectados na América do Sul e as discrepâncias entre os países desenvolvidos e em desenvolvimento com relação ao número de genomas completos depositados ao longo da pandemia. Enquanto a Europa e a América do Norte respondem por mais de 9 milhões dos genomas depositados no GISAID, a África e a América do Sul depositaram menos de 400 000 sequências genômicas. A vigilância genômica é importante para detectar sinais de alerta precoces de novos vírus circulantes, auxiliar na descoberta de novas variantes e controlar pandemias.

SARS-CoV-2 Spatiotemporal Genomic and Molecular Analysis of the First Wave of the COVID-19 Pandemic in Macaé, the Brazilian Capital of Oil.

The SARS-CoV-2 virus infection led to millions of deaths during the COVID-19 pandemic. Hundreds of workers from several other Brazilian cities, as well as from other countries, arrive daily in Macaé to work in the oil supply chain, making this city a putative hotspot for the introduction of new viral lineages. In this study, we performed a genomic survey of SARS-CoV-2 samples from Macaé during the first outbreak of COVID-19, combined with clinical data and a molecular integrative analysis. First, phylogenomic analyses showed a high occurrence of viral introduction events and the establishment of local transmissions in Macaé, including the ingression and spread of the B.1.1.28 lineage in the municipality from June to August 2020. Second, SARS-CoV-2 mutations were identified in patients with distinct levels of COVID-19 severity. Third, molecular interactions of the mutated spike protein from three B.1.1.33 local samples and human ACE2 showed higher interactions than that of the wild-type spike protein from the ancestral virus. Altogether, these results elucidate the SARS-CoV-2 genomic profile in a strategic Brazilian city and further explore the functional aspects of SARS-CoV-2 with a characterization of emerging viral mutations associated with clinical data and the potential targets for drug development against SARS-CoV-2.

Ethical, legal, and social issues in the Earth BioGenome Project.

The Earth BioGenome Project (EBP) is an audacious endeavor to obtain whole-genome sequences of representatives from all eukaryotic species on Earth. In addition to the project's technical and organizational challenges, it also faces complicated ethical, legal, and social issues. This paper, from members of the EBP's Ethical, Legal, and Social Issues (ELSI) Committee, catalogs these ELSI concerns arising from EBP. These include legal issues, such as sample collection and permitting; the applicability of international treaties, such as the Convention on Biological Diversity and the Nagoya Protocol; intellectual property; sample accessioning; and biosecurity and ethical issues, such as sampling from the territories of Indigenous peoples and local communities, the protection of endangered species, and cross-border collections, among several others. We also comment on the intersection of digital sequence information and data rights. More broadly, this list of ethical, legal, and social issues for large-scale genomic sequencing projects may be useful in the consideration of ethical frameworks for future projects. While we do not-and cannot-provide simple, overarching solutions for all the issues raised here, we conclude our perspective by beginning to chart a path forward for EBP's work.

Molecular testing and analysis of disease spreading during the emergence of COVID-19 in Macaé, the Brazilian National Capital of Oil.

The Brazilian strategy to overcome the spread of COVID-19 has been particularly criticized due to the lack of a national coordinating effort and an appropriate testing program. Here, a successful approach to control the spread of COVID-19 transmission is described by the engagement of public (university and governance) and private sectors (hospitals and oil companies) in Macaé, state of Rio de Janeiro, Brazil, a city known as the National Oil Capital. In 2020 between the 17th and 38th epidemiological week, over two percent of the 206,728 citizens were subjected to symptom analysis and RT-qPCR testing by the Federal University of Rio de Janeiro, with positive individuals being notified up to 48 h after swab collection. Geocodification and spatial cluster analysis were used to limit COVID-19 spreading in Macaé. Within the first semester after the outbreak of COVID-19 in Brazil, Macaé recorded 1.8% of fatalities associated with COVID-19 up to the 38th epidemiological week, which was at least five times lower than the state capital (10.6%). Overall, considering the successful experience of this joint effort of private and public engagement in Macaé, our data suggest that the development of a similar strategy countrywise could have contributed to a better control of the COVID-19 spread in Brazil. Quarantine decree by the local administration, comprehensive molecular testing coupled to scientific analysis of COVID-19 spreading, prevented the catastrophic consequences of the pandemic as seen in other populous cities within the state of Rio de Janeiro and elsewhere in Brazil.

Flavonoids from Siparuna cristata as Potential Inhibitors of SARS-CoV-2 Replication.

The novel coronavirus SARS-CoV-2 has been affecting the world, causing severe pneumonia and acute respiratory syndrome, leading people to death. Therefore, the search for anti-SARS-CoV-2 compounds is pivotal for public health. Natural products may present sources of bioactive compounds; among them, flavonoids are known in literature for their antiviral activity. Siparuna species are used in Brazilian folk medicine for the treatment of colds and flu. This work describes the isolation of 3,3',4'-tri-O-methyl-quercetin, 3,7,3',4'-tetra-O-methyl-quercetin (retusin), and 3,7-di-O-methyl-kaempferol (kumatakenin) from the dichloromethane extract of leaves of Siparuna cristata (Poepp. & Endl.) A.DC., Siparunaceae, using high-speed countercurrent chromatography in addition to the investigation of their inhibitory effect against SARS-CoV-2 viral replication. Retusin and kumatakenin inhibited SARS-CoV-2 replication in Vero E6 and Calu-3 cells, with a selective index greater than lopinavir/ritonavir and chloroquine, used as control. Flavonoids and their derivatives may stand for target compounds to be tested in future clinical trials to enrich the drug arsenal against coronavirus infections. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s43450-021-00162-5.

The pulmonary route as a way to drug repositioning in COVID-19 therapy.

INTRODUCTION: The outbreak of the disease caused by the new coronavirus (COVID-19) has been affecting society's routine and its patterns of interaction worldwide, in addition to the impact on the global economy. To date, there is still no clinically effective treatment for this comorbidity, and drug repositioning might be a good strategy considering the established clinical safety profile. In this context, since COVID-19 affects the respiratory tract, a promising approach would be the pulmonary drug delivery. OBJECTIVE: Identify repurposing drug candidates for the treatment of COVID-19 based on the data of ongoing clinical trials and in silico studies and also assess their potential to be applied in formulations for pulmonary administration. METHOD: A integrative literature review was conducted between June and July 2020, by extracting the results from Clinical Trials, PubMed, Web of Science and Science Direct databases. RESULTS: By crossing the results obtained from diverse sources, 21 common drugs were found, from which only 4 drugs presented studies of pulmonary release formulations, demonstrating the need for greater investment and incentive in this field. CONCLUSION: Even though the lung is a target that facilitates viral infection and replication, formulations for pulmonary delivery of suitable drugs are still lacking for COVID-19 treatment. However, it is indisputable that the pandemic constitutes a concrete demand, with a profound impact on public health, and that, with the appropriate investments, it will give the pharmaceutical industry an opportunity to reinforce the pulmonary delivery field.

Fiocruz Biological Collections: strengthening Brazil's biodiversity knowledge and scientific applications opportunities.

Biological collections are central in understanding and preserving life on Earth. In Brazil, the most representative collections are kept by natural history museums, whose primary focus is in invertebrates, vertebrates and vascular plants. Only a few institutions keep repositories in different kingdoms. The Oswaldo Cruz Foundation (Fiocruz), established in 1900, is a strategic public health institution of the Ministry of Health of Brazil. As such, Fiocruz is responsible for a wide range of activities, from basic research to the development and production of vaccines, drugs, reagents and diagnostic kits. Its biological collections were soon established in the expeditions made by naturalists and physicians seeking integrated knowledge of the fauna, flora and tropical diseases. Since then, they have been part of the institutional policy. In a few decades, those collections were already in the forefront of basic and applied research on tropical parasitic and infectious diseases. Currently, they comprise thirty-three repositories representing part of the Brazilian diversity of bacteria, fungi, protozoa, helminths, arthropods, molluscs and plants of medical and environmental importance. Different methods of long-term preservation are applied for the conservation of this wide range of organisms represented by about 6 million specimens. Herein, we describe this range of collections and discuss their complementary role as repositories of groups not represented in other biological collections in Brazil. These valuable biological materials have been used in public health and medical research, as well as for technological development and innovation in Brazil. Parallel to this specific usage, Fiocruz biological collections have played and continue to play a unique and important role in understanding and conserving part of Brazil's biodiversity that is currently under-represented in other biological and natural history collections in Brazil and South America.

Monitoring soil for sustainable development and land degradation neutrality.

The adoption of the 17 sustainable development goals (SDGs) listed in the 2030 Agenda for Sustainable Development by the United Nations urged the scientific community to generate information for planning and monitoring socioeconomic development and the underlying environmental compartments. SDGs 2, 3, 6, 11, 13, 14, and 15 have targets which commend direct consideration of soil resources. There are five groups of SDGs and assigned SDG indicators where soil plays a central role. Frameworks of soil-related sustainable development goals and related indicators which can be monitored in current monitoring schemes are proposed.

A first glance into the nutritional properties of the sea cucumber Parastichopus regalis from the Mediterranean Sea (SE Spain).

This work reports for the first time the nutritional profile, including proximate chemical composition, amino acids, fatty acids and minerals of Parastichopus regalis from the Mediterranean Sea (SE Spain). The studied species had a high moisture content, moderate protein and low lipid levels. The most abundant amino acids were glutamic acid, arginine and tyrosine. Polyunsaturated fatty acids, especially arachidonic acid, dominated the fatty acid profile. Iron, sodium, calcium and zinc were the most abundant mine rals. In general, P. regalis has a balanced nutritional quality suitable for human consumption.

The U.S. Culture Collection Network Responding to the Requirements of the Nagoya Protocol on Access and Benefit Sharing.

The U.S. Culture Collection Network held a meeting to share information about how culture collections are responding to the requirements of the recently enacted Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to the Convention on Biological Diversity (CBD). The meeting included representatives of many culture collections and other biological collections, the U.S. Department of State, U.S. Department of Agriculture, Secretariat of the CBD, interested scientific societies, and collection groups, including Scientific Collections International and the Global Genome Biodiversity Network. The participants learned about the policies of the United States and other countries regarding access to genetic resources, the definition of genetic resources, and the status of historical materials and genetic sequence information. Key topics included what constitutes access and how the CBD Access and Benefit-Sharing Clearing-House can help guide researchers through the process of obtaining Prior Informed Consent on Mutually Agreed Terms. U.S. scientists and their international collaborators are required to follow the regulations of other countries when working with microbes originally isolated outside the United States, and the local regulations required by the Nagoya Protocol vary by the country of origin of the genetic resource. Managers of diverse living collections in the United States described their holdings and their efforts to provide access to genetic resources. This meeting laid the foundation for cooperation in establishing a set of standard operating procedures for U.S. and international culture collections in response to the Nagoya Protocol.

Explanation of the Nagoya Protocol on Access and Benefit Sharing and its implication for microbiology.

Working with genetic resources and associated data requires greater attention since the Nagoya Protocol on Access and Benefit Sharing (ABS) came into force in October 2014. Biologists must ensure that they have legal clarity in how they can and cannot use the genetic resources on which they carry out research. Not only must they work within the spirit in the Convention on Biological Diversity (https://www.cbd.int/convention/articles/default.shtml?a=cbd-02) but also they may have regulatory requirements to meet. Although the Nagoya Protocol was negotiated and agreed globally, it is the responsibility of each country that ratifies it to introduce their individual implementing procedures and practices. Many countries in Europe, such as the UK, have chosen not to put access controls in place at this time, but others already have laws enacted providing ABS measures under the Convention on Biological Diversity or specifically to implement the Nagoya Protocol. Access legislation is in place in many countries and information on this can be found at the ABS Clearing House (https://absch.cbd.int/). For example, Brazil, although not a Party to the Nagoya Protocol at the time of writing, has Law 13.123 which entered into force on 17 November 2015, regulated by Decree 8.772 which was published on 11 May 2016. In this case, export of Brazilian genetic resources is not allowed unless the collector is registered in the National System for Genetic Heritage and Associated Traditional Knowledge Management (SisGen). The process entails that a foreign scientist must first of all be registered working with someone in Brazil and have authorization to collect. The enactment of European Union Regulation po. 511/2014 implements Nagoya Protocol elements that govern compliance measures for users and offers the opportunity to demonstrate due diligence in sourcing their organisms by selecting from holdings of 'registered collections'. The UK has introduced a Statutory Instrument that puts in place enforcement measures within the UK to implement this European Union Regulation; this is regulated by Regulatory Delivery, Department for Business, Energy and Industrial Strategies. Scientific communities, including the private sector, individual institutions and organizations, have begun to design policy and best practices for compliance. Microbiologists and culture collections alike need to be aware of the legislation of the source country of the materials they use and put in place best practices for compliance; such best practice has been drafted by the Microbial Resource Research Infrastructure, and other research communities such as the Consortium of European Taxonomic Facilities, the Global Genome Biodiversity Network and the International Organisation for Biological Control have published best practice and/or codes of conduct to ensure legitimate exchange and use of genetic resources.

Dataset showing the impact of the protonation states on molecular dynamics of HIV protease.

The data described here supports the research article "Unraveling HIV Protease Flaps Dynamics by Constant pH Molecular Dynamics Simulations" (Soares et al., 2016) [1]. The data involves both standard Molecular Dynamics (MD) and Constant pH Molecular Dynamics (CpHMD) to elucidate the effect of protonation states of catalytic dyad on the HIV-PR conformation. The data obtained from MD simulation demonstrate that the protonation state of the two aspartic acids (Asp25/Asp25') has a strong influence on the dynamics of the HIV-PR. Regarding the CpHMD simulation, we performed pka calculations for HIV-PR and the data indicate that only one catalytic aspartate should be protonated.

Unraveling HIV protease flaps dynamics by Constant pH Molecular Dynamics simulations.

The active site of HIV protease (HIV-PR) is covered by two flaps. These flaps are known to be essential for the catalytic activity of the HIV-PR, but their exact conformations at the different stages of the enzymatic pathway remain subject to debate. Understanding the correct functional dynamics of the flaps might aid the development of new HIV-PR inhibitors. It is known that, the HIV-PR catalytic efficiency is pH-dependent, likely due to the influence of processes such as charge transfer and protonation/deprotonation of ionizable residues. Several Molecular Dynamics (MD) simulations have reported information about the HIV-PR flaps. However, in MD simulations the protonation of a residue is fixed and thus it is not possible to study the correlation between conformation and protonation state. To address this shortcoming, this work attempts to capture, through Constant pH Molecular Dynamics (CpHMD), the conformations of the apo, substrate-bound and inhibitor-bound HIV-PR, which differ drastically in their flap arrangements. The results show that the HIV-PR flaps conformations are defined by the protonation of the catalytic residues Asp25/Asp25' and that these residues are sensitive to pH changes. This study suggests that the catalytic aspartates can modulate the opening of the active site and substrate binding.